[2] Open civil war between the emperors broke out in 316, when Constantine invaded Licinius' Balkan provinces.

After his crushing defeat at the Battle of Cibalae on October 8, 316[3] (some historians date it in 314),[4] Licinius fled to Sirmium then further south to Adrianople.

There he collected a second army, under the command of an officer named Valerius Valens whom he raised to the rank of augustus.

Simultaneously he tried to negotiate, but Constantine, insulted by the elevation of Valens and confident from his recent victory, rejected the peace offer.

A critical point might be when he received news of a sudden enemy raid that captured his baggage and the royal entourage.